Electric starter.



A. HLMIDGLEY.

ELECTRIC STARTER.

APPLlcmnN min uw 1o. ma.

1,274,575. PatentedAug.'6,191a.

Wi .esse 1 r .Mw

.with the armature; '1

UNITED STATES PATENT OFFICE.

ALBERT HENRY MIDGLEY, OF ACTON VALE, ENGLAND, ASSIGNOR OF ONE-HALF T0 CHARLES ANTHONY VANDERVELL, 0F ACTON VALE, ENGLAND.

ELECTRIC STARTER.

peeicatlon of Letters Patent.

Patented Aug. 6,1918.

Application Bled July 10, 1915. Serial No. 39,184.

lEngland, have invented certain new and uscfu] Improvements in and Relating to E1ec tric Starters, of which the following is a specification.

This invention relates to an improved electric starter for internal combustion engines such as used on motor cars or the like, and of the kind in which use is made of a displaceable armature for coupling the shaft of the electric motor with the engine shaft and the displacement of which armature is effected by the axial pull exerted thereon by the field magnet.

In electric starters of the kind above l'eferred to, the field is first strongly energized and the maximum current tiowing through the armature reduced, until the shaft of the electric motor has been coupled with the engine shaft, whereupon the full working current is pass-rd through the armature, and this has hitherto been attained by utilizing one and thel same thick wire series winding for energizing the Iield before and after the coupling, said winding being used, owing to its low resistance, in series with a resistance to prevent short-circutiug of the battery, and by reducing,r the current. fiowing through the armature before the coupling by means of a resistance inserted inY shunt he electric energy consumed by the rcsistances referred Vto is not converted into any useful work andtherefore constitutes a loss, and the main object of the present invention is to provide an improved arrangement by which this disadvantage is overcome while insuring at the sinne time a strongenergization of the field during the coupling'period of the starting operation without the battery being shorteircuited.

By the use of many turns of thin wire during the first step of the starting operation, the Held magnet is strongly mngnetized, whereby a strong axial pull' is exerted upon the armature while the voltage across the armature is thereby greatly reduced and the rotation imparted to the armature is consequently very slow. It will also be seen that in spite of the strong magnetization ot' the field magnet during this step of the starting operation, the current taken from the battery-and fiowin through the field excitation windings o? the armature is greatly reduced as compared with the nor mal working current of the motor during the last part of the starting operation when the armature rotates to start the engine.

Figures 1 to 3 of the accom ings illustrate diagrammatica ly and by way of example three different modes of carryingr the invention into effect.

Referring to Fig. 1, a. is the armature which is displaceahly mounted in the frame I; of the motor, its shaft being coupled with the shaft r: of thc engine to be started by means of a toothed gear, the members (l and c of which are mounted on the armature shaft and on the liywheel of the engine respectively. Each of the poles g of the motor is provided with a. thick wire windin It, and a thin wire winding i, similar to t ose of a series and shunt winding respectively, these windings being connected to the main brushes j of the motor and with the battery Z through the` intermediary of a switch m provided with two contact arms m, and m2.

The operation of the starter is as follows: 1When the switch -m is moved so that the arm lm.2 makes contact with the stationary contact o. the poles r/ are excited by means of the thin wire winding 'i and thick Wire winding g which is arranged in series with the thin wire winding z' and in series with the armature a, whereby the armature is drawn into the field in order to bring the members d and e of the gear into engagement with cach other. After the couplin of the armature shaft with the engine sha t. through the intermediary of the gear, the switch m is shifted in such a position that the contact arm m2 makes contact with the stationary contact 71 whereby the thin wire winding I is disconnected from the circuit and thethick wire winding li is left in series with the armature, the motor now running as an Ordinar series motor. A further movement of t e switch m. brings the contact arm m, into contact with the stationary Contact 0 thev contact arm m, remaining in contact with the stationary contact pz, whereby the thin wire winding z' is connected across the battery and the motor thus caused to operate as an ordinary compound motor.

ifVhen the engine starts to rotate under its own power, the magnetization of the field anying drawingin exciting 'in Fig. 2,

decreases and the armature a is axially moved in a direction opposite to that in which it moved durin the starting operation either by means o a spring f arranged as s own on the drawing, or by other suitable means which will cause the disengagement of the. gea'r. For instance, the colplingand uncoupling of the armature an engine shafts mag' be effected by means of the spiral ear re erred to in my application Serial o. 9717.

Referrn tothe modification illustrated ie first movement of the switch m causes-the thin wire winding i to he inserted in series with the armature and in series with the thick wire winding It, whereupon the thin wire winding z' is disconnected, the machine now runningr as an ordinary series motor with the thick wire `winding h in series with the armature and the battery.

In the modification illustrated in Fig. 3, the magnetic field is first excitedl by the two windin h and z' in series with one another until the coupling of the armature shaft with the engine shaft has been effected, whereu on the' thin wire winding is dsconnecte the mnchinenow running` as an ordinary series motor with the thicc` wire winding h in series with the armature. A further movement of the switch m causes the thin wire 'winding c' to be inserted in parallel with the thic wire winding h, the machine now running as a series motor with two windings in parallel with each other.

The two windings h and when used simultaneously in the various modifications above referred to may be arranged to act differentially'nstead of in the same sense.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. A method of starting an internal combuston engine by means of an 4electric motor through the intermediary of a gear, one member of which is mechanically attached to the engine and the other member thereoftoan axially displaceable armature of the motor which is drawn into the'field by the magnetizationof the poles, consistthe field by means of two excitation coils, the number of turns and the total resistance of the one coil being substantially eater than the number of turns and tota resistance of the other coil, the field being excited first by means of the two excitation coils in series with each other and with the armature and source of energy, and then by the excitation coil having tie smaller number of turns and the smaller total resistance in 'series with the armature and source of current, as and for the purpose set forth.

2. A method of starting an internal combustion engine by means of an electric m0- tor through the intermediary of a gear, one member of which is mechanically attached to the engine and the other member thereof to an axially displaceable armature of the motor which is drawn into the field hy the magnetization of the poles, consisting in exciting the field by means of two excitation coils, the number of turns and the total resistance of the one coil being substantially greater than the number of turns 4and total resistance of the other coil, the field being excited first by means of the two excitation coils in series with each other and with the armature and source of energy, then by the excitation coil having the smaller number of turns and the smaller total resistance in series with the armature' and source of current, and finally also by the other excitation coil, as and for the purpose setV forth.

3. A method of starting an internal combustion engine by means of an electric motor through the intermediary of a gear, one member of which is mechanically attached to the engine and. the other member thereof to an axially displaceable armature of the motor which is drawn into the field by the magnetization of the poles, consisting in exciting the field by means of two excitation coils, the number of turns and the total resistance of the one coil being substantially greater thathe number of turns and total resistance of the other coil, the lfield being excited first by means of the two excitation coils in series with each other and with the armature and Vsource of energy, then by the excitation coil having the smaller number of turns and the smaller total resistance in series with the armature and -source of curi-ent, the other excitation coil being disconnected and finally also by the latter excitation coil which is corinected across the battery, as and for the purpose set forth.

In testimony whereof I have signed my nume to this specification.

ALBERT HENRY MIDGLEY.

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